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MCQIntermediateStars & Stellar Evolution
USAAAO — 2026 First Round
Question 28
Below is an HR diagram for a globular cluster from Gaia DR3 data. The figure has labeled regions: “A”, “B”, “C”, and “D”. 1) Identify the region where stars undergo hydrogen burning in their cores. 2) Identify the region where stars experience Helium flash.
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Source
USAAAO 2026 First Round, Question 28. Question text, choices, and answer were transcribed from the official USAAAO exam and solutions PDFs. Official HR diagram omitted; consult cited exam page.